*{
    margin: 0;
    padding: 0;
}
li{
    list-style: none;
}
a{
    text-decoration: none;
}
.clearfix:before,.clearfix:after {
    content:"";
    display:table;  /* 这句话可以出发BFC BFC可以清除浮动,BFC我们后面讲 */
}
.clearfix:after {
    clear:both;
}
.clearfix {
    *zoom:1;
}
.fl{
    float: left;
}
.fr{
    float: right;
}